<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            color: yellow;
        }
    </style>
</head>
<body>
    <div>div</div>
    <div class="box"></div>
    <div id="box">id</div>

    <ul>
        <li>12</li>
    </ul>
    <script>
        const obj = {
            name : '张三'
        }
        obj.name = '李四'

        const box = document.querySelector('.box')
        box.innerHTML = '<strong>你好</strong>'
    </script>
</body>
</html>